Device for continuous casting of refractory materials



P. BLUM ET May 6, 1969 DEVICE FOR CONTINUOUS CASTING OF REFRACTORY MATERIALS D w E 3 m A u u f V L 0 m8 H ED a w v C W 5 on 4 2 I i. m I f w. 9 A r P G m .ll. 1 ll 6 r .E F r E l W E I H F5 8 w m J d e l i F ATTORNEYS May 6, 1969 P. BLUM ETAL 3,442,321 DEVICE FOR CONTINUOUS CASTING OF REFRACTORY MATERIALS Filed June 1, 1966 Sheet 2 of 3 INVENTORS 1 /5995 54 m7 JACQUES DEV/LLAED BY 46% ATTORNEYS P. BLUM ETAL 3,442,321

May 6, 1969 DEVICE FOR CONTINUOUS CASTING OF REFRACTORY MATERIALS Sheet Filed June 1, 1966 H II II II III II II II INVENTORS ID/ERRE 841/47 United States Patent 3,442,321 DEVICE FOR CONTINUOUS CASTING OF REFRACTORY MATERIALS Pierre Blum and Jacques Devillard, Grenoble, Isere, France, assignors to Commissariat a lEnergie Atomique, Paris, France Filed June 1, 1966, Ser. No. 554,530 Claims priority, applicatigrgzFrance, June 3, 1965,

Int. Cl. B22ti 27/01, 11/06; B281) 3/12 US. Cl. 164-250 8 Claims ABSTRACT OF THE DISCLOSURE Continuous casting of refractory materials such as uranium carbide, for example, is usually carried out by subjecting the material to the beam of an electron gun inside a water-cooled copper crucible. The bottom of the crucible is movable and consequently makes it possible to maintain the bath at a constant level within the crucible. The casting skin which is in contact with the cold walls of the crucible solidifies and acquires sufficient strength to contain the liquid phase which has not yet solidified.

The structural soundness of the material is nevertheless improved if the ingot is caused to rotate together with its crucible beneath a stationary electron beam and beneath stationary means for supplying granular material. By means of this process, better distribution of the solid phase can be ensured at the level of the bath. Consequently, any heterogeneity of the electron beam is not liable to give rise to overheating of the electron beam is not liable to give rise to overheating points which would in turn result in a basalt-type structure with extensive crack formation. On the other hand, substantial local projections are liable to adhere to the surface of the crucible and thus to interfere with the drawing process.

By means of these differential methods, it is possible to obtain what may be termed calm fusion which is particularly desirable in drawing ingots which have a small diameter. However, there remains a permanent physical phenomenon which interferes with a continuous casting to a considerable extent after a few minutes of operation, and this is the evaporation of the material which results in more or less rapid accumulation of a troublesome layer on the walls of the cold crucible.

The aim of this invention is to eliminate this phenomenon by means of a continuous renewal of the wall of said crucible.

The invention accordingly has for its object a casting device of the type comprising an electron gun which is disposed axially above a crucible having an axially movable base and a device for the continuous introduction of material to be melted in the eletcron beam, characterized in that the crucible is provided with a side wall which is endowed with uniform motion and is continuously replaced by an identical wall.

In accordance with a further characteristic feature, this device comprises two movable members which are adapted to rotate about axes located at right angles to the ice axis of the crucible said movable members being mounted in adjacent relation and provided with identical grooves forming a circular gap for casting metal at the points of contact of said two movable members.

In a preferred embodiment, the movable members are grooved pulleys which has axes at right angles to the axis of the crucible and which are in contact along one of their generatrices.

The circular gap between the grooves thus forms conjunction with the base a melting pot having a side wall which is renewed progressively as the movement of the pulleys takes place. The crucible wall leaves the melting point before any troublesome deposit has had time to form, and is progressively replaced by a fresh wall. Consequently, the melting process always takes place in a crucible which has a clean wall.

A number of other properties and advantages of the invention will in any case become readily apparent from the following detailed description which is given by way of non-limitative example, reference being had to the accompanying drawings, in which:

FIG. 1 shows partly in side view and partly in axial cross-section a casting device in accordance with the invention;

FIG. 2 is an overhead plan view of the crucible which is employed in the device of FIG. 1;

FIG. 3 is an axial sectional view of an alternative form of construction of the casting device;

FIG. 4 is an overhead plan view of the crucible of said alternative form of construction.

The casting device as a whole is placed within a leaktight chamber which has not been shown in the drawings. There are fixed within said chamber an electron gun I and a conduit 2 for supplying the material to be melted. The axis of said conduit is inclined to the axis of the electron beam 3 which is delivered 'by the gun I in order that the particles of material should be introduced at the center of said beam.

Below said gun I, a plunger 4 is adapted to move axially between two identical pulleys 6, 8 which are mounted side by side and which are tangent to each other at 10 along one of their generatrices. At this point of contact, the grooves 7, 9 of the pulleys 6, 8 form an annular gap 12 having a diameter which corresponds to that of the plunger 4 and consequently of the ingot to be formed.

The pulleys 6, 8 are rotatably mounted on shafts 14, 16 which are at right angles to the plunger 4 and carried by end-plates 18 which are rigidly fixed to a base 20. The stem 22 of the plunger 4 is adapted to pass through the center of said base 20 and to slide freely with respect to this latter.

Conduits 24, which are connected to a circuit (not shown in the drawings) for circulating a coolant such as water, pass through the shafts 14 and 16 and thus effect the cooling of the pulleys 6 and 8 which are preferably formed of copper but can also be constructed of any like material. During the casting operation, said pulleys are driven in rotation in opposite directions as shown by the arrows of FIG. 1 by means of any suitable system such as pulleys, pinions or the like which are fixed on the shafts 14 and 16 and driven by a single motor.

In the example of construction which is illustrated, each pulley 6, 8 is rigidly fixed to a toothed pinion 17, 19 (FIG. 2) and one of said pinions, namely the pinion 19, is in mesh with a pinion 21 which is driven by a motor 23. The pinion 19 is coupled with the pinion 17 by means of a rack 25 having two parallel sets of teeth; the pinions 17 and 19 and consequently the pulleys 6 and 8 therefore rotate in opposite directions. The rack 25 is secured to the plunger 4 by means of an arm 27, with the result that the movement of rotation of the 3 pulleys causes the said plunger 4 to slide with respect to the base 20.

The crucible 12 is thus constituted on the one hand by the wall of the grooves 7 and 9 at the tangential point 10 or point of contact of the pulleys, said wall being continuously withdrawn and replaced while remaining identical with itself and, on the other hand, by the plunger 4 which forms a movable base and accordingly recedes from said wall progressively as the ingot is formed, said pulley grooves and said plunger being displaced at the same time in a synchronized movement.

At the time of introduction of granular particles 26 of the material to be melted in the beam 3 of the electron gun, the molten material is cast in said crucible 12 which is cooled by circulation of fluid within the conduits 24.

As it solidifies, said material forms a cylindrical ingot 28 as shaped by the grooves 7 and 9 and the casting skin in particular becomes sufiiciently strong to dispense with any further need of lateral support. As it moves with respect to the base 20, the plunger therefore extracts the ingot 28 from the gap 12 in a progressive manner while the pulleys 6 and 8 rotate, thereby progressively moving said ingot away from the walls of the grooves 7 and 9 which have just been in contact with the molten material and bringing into contact a clean portion of the same grooves which progressively re-forms the crucible 12.

The speed of rotation of the pulleys is preferably very low, for example 10 to millimeters per minute in tangential velocity, so as to enable the ingot to form normally but remains sufficiently high to prevent any possibility of evaporation to an extent which might result in the formation of a troublesome layer on the walls of the grooves. The movement of the plunger and consequently the rate of extraction of the ingot is dependent on said tangential velocity, which is dependent in turn on the nature of the material and on the diameter of the ingot to be obtained.

The homogeneity of said ingot is even further improved when the complete crucible assembly is driven in rotation, which results in a better distribution of the particles at the surface of the bath. With this object in mind, the assembly consisting of base 20 and pulleys 6, 8 which is rigidly coupled for rotation with the stem 22 of the plunger 4 by means of the rack 25 or, in other words, the assembly consisting of all the components of the crucible 12, is driven in rotation about the axis of said plunger, for example by means of a set of teeth 31 (FIG. 1) which is carried by the base 20 and engaged with a pinion 29 which is driven in rotation by a motor 30.

In accordance with an alternative form of construction which is illustrated in FIGS. 3 and 4, the grooved pulleys 32, 34 which constitute the side wall of the crucible are provided with one or a number of teeth 36 (three in the case of the example shown in the figure) which partially close the groove 33, 35 and form a throttled section of the crucible. The ingot 38 is consequently provided at uniform intervals with necked portions which make it possible to break off the ingot in sections without difficulty.

In this case, the casting operation is preferably carried out as a continuous process. This can readily be ensured since the bottom of the crucible is constituted by the metal which has just set. Each ingot section which is formed can thus be detached as it is delivered from the crucible and no longer needs to be supported. A plunger or like member is employed only at the beginning of the casting operation so as to provide the crucible with an initial base or end-wall and is then dispensed with, the ingot being first driven down by the teeth 36 and then displaced as a result of the motion of the pulleys themselves.

The pinions 37 and 39 which are rigidly fixed to the pulleys 32 and 34 are then directly engaged with each other (FIG. 4) whilst one of said pulleys, namely the pulley 39, is engaged with a pinion 41 which is driven by a motor 43.

The base 20 which supports the pulleys is driven in rotation in the same manner as in the previous example and the wall of the crucible rotates about the axis of this latter. The base 20 is pierced by a central bore 44 through which the ingot 38 can slide freely until it reaches a point located opposite to a breaking-off device of any known type (tongs or the like).

In certain cases, when the ingot is intended to be of fairly substantial length or when it is desired to make use of the device in an absolutely continuous manner, provision can be made on each of the pulleys 6 and 8 or 32 and 34, for example at a point which is diametrically opposite to the tangential point 10, for a system such as a brush, scraper or like system, not shown, for the purpose of cleaning the bottom of the grooves 7, 9 or 33, 35.

By this means, cleanliness of the grooves is ensured when these latter reach the tangential point and both the shape and dimensions of the crucible 12 are maintained constant, which accordingly makes it possible to obtain an homogeneous ingot having a uniform shape.

The diameter of the pulleys can also be fairly substantial in order that the draw-taper which is provided by the radius of curvature is not excessive and that the height or length over which the ingot solidifies is substantially rectilinear.

As will be readily understood, a number of different modifications could be made in the mode of construction which has just been described by way of example without thereby departing from the scope of the invention. For example, the movable members could be endowed with any shape which is designed to permit of uniform displacement of the grooves above the plunger.

What we claim is:

1. A device for continuously casting granular refractory materials into an ingot, comprising:

a crucible in which the granular refractory materials to be cast are melted and subsequently cast into a continuous ingot, said crucible having an axially movable base;

means for continuously introducing the granular refractory materals into said crucible;

an electron gun disposed above said crucible for continuously melting granular refractory material in the crucible;

means for cooling the side wall of the crucible for forming into a casting skin the portion of the molten refractory material in contact therewith; and means for moving the cooled side wall of the cnucible with a uniform motion equal in speed to that of the ingot being formed therein, whereby the cooled side wall is continuously replaced by an identical wall.

2. A continuous-casting device in accordance with claim 1, characterized in that the crucible side wall comprises two movable members which are adapted to rotate about axes located at right angles to the axis of the crucible, said movable members being mounted in adjacent touching relation and provided with identical grooves forming a circular gap defining the crucible side wall for castng metal at the points of contact of said two movable members 3. A continuous-casting device in accordance with claim 2, characterized in that the movable members are grooved pulleys which have axes at right angles to the axis of the crucible and which are in contact along one of their generatrices. i 4. A continuous-casting device in accordance with .Iclaim 3, characterized in that the movable members are carried by a base which is rotatable about the axis of the crucible.

5. A continuous-casting device in accordance with claim 4, characterized in that the base which carries the mov- 5 able members is rigidly coupled for rotation with a plunger which constitutes the ba-se of the crucible.

6. A continuous-casting device in accordance with claim 3, characterized in that a cooling fluid is. circulated through the hub of each pulley.

7. A continuous-casting device in accordance With claim 3, characterized in that said device comprises means for driving the base of the crucible which are controlled in dependence on the speed of displacement of the movable members.

8. A continuous-casting device in accordance with claim 3, characterized in that the groove of each pulley comprises at least one tooth for partially closing the crucible.

References Cited UNITED STATES PATENTS 3,388,736 6/1968 Accary et a1 164-50X 441,375 11/1890 Norton et a1 164-87 X FOREIGN PATENTS France. France. Germany. Germany. Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner. 15 R. SPENCER ANNEAR, Assistant Examiner.

US. Cl. X.R. 

